Year	Kg per Square Metre
1980	25.75
1981	25.9
1982	26.04
1983	26.16
1984	26.27
1985	26.36
1986	26.45
1987	26.57
1988	26.69
1989	26.82
1990	26.96
1991	27.1
1992	27.27
1993	27.45
1994	27.61
1995	27.77
1996	27.92
1997	28.07
1998	28.22
1999	28.37
2000	28.54
2001	28.7
2002	28.87
2003	29.05
2004	29.21
2005	29.36
2006	29.51
2007	29.66
2008	29.82